On September 27, I bought a Gigabyte AORUS Radeon RX 580 8GB Graphic Cards on Amazon to verify that you were in the promotion with Assassin's Creed® Odyssey, Strange Brigade®, and Star Control®: Origins and after a couple of weeks I still do not receive the coupon by mail. Here the link where a purchased my graphic card Amazon.com: Gigabyte AORUS Radeon RX 580 8GB Graphic Cards GV-RX580AORUS-8GD: Computers & Accessorie... and if you need the reciepe and can send you to the support e-mail.
Have a good day.
You must get the coupon from Amazon to be able to redeem it at AMD REWARDS.com
Here is a current thread here concerning the problems Users are having getting their Coupons from Retailers: Raise the Game bundle did not come with my RX 580